In conventional construction materials and in window and door manufacture, vinyl, vinyl composite, wood and metal components are used in forming structural members. Most commonly siding, trim, window or door units are typically made from extruded vinyl or aluminum or milled wood members. Such materials and units made of these materials, require maintenance and are often energy inefficient. Vinyl materials have been used in forming envelopes, profile and seal components in window units. Such vinyl materials typically comprise a major proportion of vinyl polymer with inorganic pigments, fillers, lubricants, etc. Extruded or injection mold of thermoplastic materials have been used, filled and unfilled as flexible and rigid thermoplastic materials used in seals, trims, fasteners, and other window construction parts. Thermoplastic polyvinylchloride has been combined with wood members in the manufacture of PERMASHIELD.RTM. brand windows manufactured by Andersen Corporation for many years. The technology is disclosed in Zaninni, U.S. Pat. Nos. 2,926,729 and 3,432,885. Generally, PVC materials is used as a cladding or coating. The PVC technology used in making PERMASHIELD.RTM. brand windows involve extruding or injection molding thin polyvinylchloride coating or envelope onto a shaped wooden structural member. One useful alternative to vinyl envelopes around wood members is a polyvinylchloride wood fiber composite such as that disclosed in patents assigned to Andersen Corporation including U.S. Pat. Nos. 5,406,768; 5,441,801; 5,486,553; 5,539,027; 5,497,594; 5,695,874; 5,518,677; 5,827,607 and published European Patent Application No. 586,212, and others.
Polyolefin materials such as polyethylene and propylene, common polyolefin compositions, have been available in a variety of grades and forms for many years. In large part, polypropylene has not been used in exterior applications or as exterior structural members due to its limited structural capacity and its inability to resist the damaging effect of weather, typically heat, light and cold. Recently, polypropylene has been used in a variety of applications in which the polypropylene is combined with a reinforcing composition in a variety of ways. For example, Shinomura, U.S. Pat. No. 3,888,810, teaches a thermoplastic composite comprising a thermoplastic resin, fibrous materials and preferably synthetic or natural rubbers. Jones, U.S. Pat. No. 3,917,901, teaches a conductor having an insulative layer comprising a polyolefin-wood composite. Nakano et al., U.S. Pat. No. 3,962,157, claim a polypropylene composition modified with a porous filler and a free radical agent that promotes reaction between the filler and the polymer. Laver, U.S. Pat. No. 5,516,472, claims an apparatus and method for making a composite which forms, internally, pellet-like strands that are then recombined to form an extruded part. Bainbridge et al., U.S. Pat. No. 5,766,395, claim a self-supporting composite structure in the form of a panel made by compression molding composite materials. The prior art also discloses a large proportion of patents that compatibilize a combination of a polyolefin with a cellulose filler using such materials as plasticizers, monomeric silicone containing compounds, grafted silyl moieties on either the polymer or the filler, polyolefin lubricants, blends of varied types of polymers in combination with the primary polyolefin, synthetic elastomers and rubbers, methylol phenolic modified polyolefins, blends of ethylene polymers and polypropylene polymers, in situ polymerization of monomers onto a fiber used in the making of a composite, specialized fibers including polytetrafluoroethylene fibers, expanded or otherwise specially modified polyolefins, glyoxal and other types of thermally reactive crosslinking agents, modified cellulosic fibers including the use of metals, crosslinking agents, compatibilizing agents, etc. Wold, U.S. Pat. No. 5,435,954, teaches a molding method for forming a composite into a useful article.
The polypropylene art has shown significant advancement and sophistication in learning to obtain new physical properties from polypropylene, various fibers and reagents or other polymers. Representative examples of recent developments in the manufacture of polypropylene compositions, particularly metallocene catalyst manufactured propylene, is shown in the technical literature owned by Montell North America Inc. For example, Malucelli et al., U.S. Pat. No. 5,574,094, teach improved polyolefin compositions comprising one or more crystalline materials having a melt index higher than 20 grams-10 min.sup.-1 combined with a cellulosic particle or fiber. Malucelli et al. disclose pelletizing such a composite and converting such a pellet into products by way of injection molding. Sacchetti et al., U.S. Pat. No. 5,691,264, disclose a bimetallic metallocene catalyst containing at least one M-.pi. bond combined with a support comprising magnesium halide in the gas phase polymerization of an olefin such as propylene into a structural polymeric product. In particular, these catalysts obtain the polymerization of olefins such as propylene into high molecular weight useful materials. The patent literature describes bimetallic catalysts comprising a compound of titanium or vanadium supported on a magnesium halide reactive with a metallocene compound containing at least one cyclopentadienyl ring coordinated on a transition metal selected from V, Ti, Zr, Hf, or mixtures thereof. Examples of such catalysts are described in U.S. Pat. No. 5,120,696, EP-A-447070 and EP-A-447071. The bimetallic catalysts can be obtained by impregnating a silica support with a magnesium compound of the type MgR.sub.2, wherein R is a hydrocarbon radical and then reacting the treated support with a compound of Ti, such as TiCl.sub.4, optionally with SiCl.sub.4 and thereafter with a metallocene compound. Such materials are shown in EP-A-514594. Such bimetallic catalysts obtained by these treatments and then with other titanocenes such as dicyclopentadienyl titanium dichloride and bis(indenyl) titanium dichloride are shown in EP-A-412750. Similar catalysts obtained by treating carbonated compounds of magnesium such as alkyl magnesium carbonate, with titanium dichloride in the presence of a metallocene compound of Hf or Zr, are known from PCT Application WO 94/03508. Bimetallic catalysts comprising a titanium based catalyst in which the Ti compound is supported on a Mg halide, a metallocene compound and a poly(methylaluminoxane) (a MAO) are disclosed in EP-A-436399. Sacchetti et al., U.S. Pat. No. 5,698,487, disclose additional compositions and methods for preparation of metallocene catalysts for preparing polyolefin materials. Govoni et al., U.S. Pat. No. 5,698,642, disclose a particular gas phase polymerization project having two interconnected polymerization zones for olefin polymerization. Sacchetti et al., U.S. Pat. No. 5,759,940, disclose further information on the preparation of catalytic materials for the manufacture of polyolefin materials. Additional details for manufacturing modem metallocene catalysts are shown in U.S. Pat. No. 4,542,199 and EP-A-129368; EP-A-185918; EP-A-485823; EP-A-485820; EP-A-51237; and U.S. Pat. Nos. 5,132,262; 5,162,278; 5,106,804. The more modern polypropylene polymeric materials show improvement in physical properties when compared to the materials made using the initially formulated Zigler-Natta catalytic materials developed since the early 1960's.
Kourgli, U.S. Pat. No. 5,542,780, discloses a polypropylene composite having an elastic modulus of about 500,000 or less. Coran et al., U.S. Pat. No. 4,323,625, teach a polypropylene composite having 20 wt % of a hardwood pulp and a modulus less than 200,000. Nishibori, U.S. Pat. No. 5,725,939, teaches a wood meal polypropylene composite with 50% polymer and a modulus less than 400,000. Beshay, U.S. Pat. No. 4,717,742, discloses an aspen pulp polypropylene composite having 40 wt % pulp and a tensile modulus less than 100,000. Beshay, U.S. Pat. No. 4,820,749, teaches an aspen pulp polypropylene composite having about 40 wt % pulp and a modulus of less than 100,000. Dehennau et al., U.S. Pat. No. 5,164,432 and Bortoluzzi et al., U.S. Patent No. 5,215,695, show sawdust containing composites with less than 50 wt % fiber and a modulus less than 800,000. Malucelli et al., EP Application No. 540026, teach a wood flour polypropylene composite having 50 wt % polymer and a modulus less than 700,000. In summary, the prior art relating to polypropylene composites typically uses 50 wt % or less fiber, exhibits a modulus of less than 800,000 and is not particularly descriptive regarding manufacturing process conditions or valuable thermal or structural properties. The industry has not succeeded in manufacturing a high strength and thermally stable composite. The industry has failed to prepare a complex thin-wall profile structural member from polypropylene and a reinforcing fiber that can show structural integrity over the life of a fenestration unit.
A substantial need exists for an improved polyolefin-wood fiber composite structural material that can be extruded into a weatherable, color stable, engineering structural member. Such a structural member requires physical stability, color stability, a controllable coefficient of thermal expansion and sufficient modulus to survive in a construction installation and while exposed to the exterior environment. The composite must be extruded or extrudable into a shape that is a direct substitute in assembly properties and structural properties for a wooden or extruded aluminum member. Such materials must be extrudable into reproducible, stable dimensions and useful cross-sections with a low heat transmission rate, improved resistance to insect attack, improved resistance to water absorption and rot resistance when in use combined with hardness and rigidity that permits sawing, milling and obtains fastening retention properties comparable to wood members and aluminum members. Accordingly, a substantial need exists for further developments in the manufacture of composite members for fenestration units.